Gas turbine engines, such as those used to provide thrust to an aircraft, are internal combustion engines that utilize air as the working fluid. Gas turbine engines extract chemical energy from fuel and convert it into mechanical energy which may be used to propel an aircraft or to provide power for other applications. A gas turbine engines typically includes a fan section, a compressor section (including a low pressure compressor and a high pressure compressor), a combustor (or combustors), and a turbine section (including a high pressure turbine and a low pressure turbine), each positioned sequentially in an upstream to downstream arrangement.
During operation, air may be drawn into the engine and accelerated by the fan section. A portion of the indrawn air may then be directed through the compressor section, the combustor(s), and the turbine section. More specifically, this air may first be pressurized in the compressor section and then combusted in the combustor(s) to produce hot combustion gases which may expand through and drive the high pressure turbine and the low pressure turbine which may, in turn, drive the rotation of the compressor section and the fan section as all may be mounted on an interconnecting shaft. The air may then be exhausted through an exhaust nozzle to provide thrust to an aircraft or to provide power if used in land-based operations.
In order to assess the operation efficiency of a gas turbine engine, as well as the performance of gas turbine engine components, it may be necessary to monitor the temperature of gases flowing through the compressor section, the combustor(s), and/or the turbine section, as well as other regions of the gas turbine engine. Some gas turbine engine designs use thermocouples as temperature sensors for this purpose. For example, temperature monitoring of air/gases flowing through a gas turbine engine may be achieved by placing a thermocouple temperature sensor at one or more stations of interest such as the inlets or the outlets of the low pressure compressor, the high pressure compressor, the combustor, the high pressure turbine, and/or the low pressure turbine. For example, as described in U.S. Pat. No. 8,478,473, a gas turbine engine was instrumented with a plurality of thermocouples to monitor turbine temperatures. While effective, some thermocouple-based temperature sensors may suffer from temperature measurement errors caused by heat transfer and variations in wire sensitivity.
Phosphor thermometry is a highly sensitive temperature sensing technique that offers temperature measurement precision as fine as 0.01° C. This technique may involve exciting a phosphor with an excitation light and monitoring the decay kinetics of the fluorescence emission signal that is subsequently emitted by the phosphor. More specifically, an accurate temperature measurement may be made from a measurement of the phosphor's fluorescence decay constant which may have a known correlation with temperature. However, some existing phosphor thermometry systems may use complex components such as “Y-couplers” for providing branching points along signal transmitting waveguides and/or for separating the excitation light from the fluorescence emission signal. Such components may be technically challenging to operate and may increase the space requirements for the phosphor thermometer. At least for the purposes of reducing packaging space, sensor design complexity, and manufacturing costs, there is a need for improved designs for phosphor thermometers.